The World Wide Web (also known as the “Web”) and the web pages within the Web are a vast source of factual information. Users may look to web pages to get answers to factual questions, such as “what is the capital of Poland” or “what is the birth date of George Washington.” Web search engines, however, may be unhelpful to users in this regard, as they generally do not provide a simple, succinct answer to factual queries such as the ones described above. Rather, Web search engines provide to the user a list of Web pages that are determined to match the query, and the user has to sort through the matching Web pages to find the answer.
Attempts that have been made to build search engines that that can provide quick answers to factual questions have their own shortcomings. For example, some search engines draw their facts from a single source, such as a particular encyclopedia. This limits the types of questions that these engines can answer. For instance, a search engine based on an encyclopedia is unlikely to be able to answer many questions concerning popular culture, such as questions about movies, songs or the like, and is also unlikely to be able to answer many questions about products, services, retail and wholesale businesses and so on. If the set of sources used by such a search engine were to be expanded, however, such expansion might introduce the possibility of multiple possible answers to a factual query, some of which might be contradictory or ambiguous. Furthermore, as the universe of sources expands, information may be drawn from untrustworthy sources or sources of unknown reliability.